The present invention relates to a method and apparatus for making a low density foam from a polyester resin and more particularly to a method and apparatus for depositing an uncured polyester resin onto a surface to form a foamed polyester resin article.
Techniques have been available for producing polyester resin foams. While the prior techniques purport to produce low density foams, the techniques have only been successful in producing foams having a density of greater than twenty-four pounds per cubic foot. Additionally, these prior techniques are successful in making such foams only on a substantially horizontal surface or in a mold. Examples of such polyester resin foams are those disclosed in three patents to Jacobs et al., U.S. Pat. Nos. 3,920,589, 3,920,590, and 3,920,591. These foam compositions have, however, led to limited commercial interest because of their high cost and impracticality. Moreover, attempts to spray these foams onto a surface or place them into a mold have not always been successful.
Recent advances have been made in connection with low density polyester resin foam utilizing a sulfonyl hydrazide blowing agent in conjunction with promoters, surfactants and other materials. Such foamed resins are disclosed in West et al., U.S. Pat. No. 4,327,196. Attempts to spray even these improved resin foams have also met with limited success, especially when attempts have been made to spray the resin foam with or without glass fiber reinforcement onto a surface that has a vertical component.